From the prior art, there has been known a microstrip antenna in which an antenna electrode and a ground electrode are respectively provided upon the surface and upon the rear surface of a substrate; and a radio wave in a vertical direction from the antenna electrode is generated by a high frequency microwave signal being applied between the antenna electrode and the ground electrode. The following techniques are known for controlling the direction of the integrated radio wave beam which is generated from the microstrip antenna. For example, with the technique described in Japanese Laid-Open Patent Publication Heisei 7-128435, a plurality of antenna electrodes are disposed upon the surface of the substrate, and the direction of the integrated radio wave beam is changed by changing the length of the feed line of the high frequency signal to each of these antenna electrodes, by switching over a high frequency switch. In other words, by the length of the feed lines to the plurality of antenna electrodes being different from one another, a phase difference is created between the radio waves which are emitted from each of the plurality of antenna electrodes, so that the integrated direction of the integrated radio wave beam is inclined towards that one of the antennas whose phase has been delayed. Furthermore, with the technique described in Japanese Laid-Open Patent Publication Heisei 9-214238, a plurality of antenna electrodes are arranged so that the directivities of their integrated radio wave beams are different, and the direction of the integrated radio wave beam is changed, by changing over the antenna electrode to which the high frequency signal is applied with a high frequency switch.
A body detection device which uses a radio wave generated from a microstrip antenna is known. With this body detection device, by changing the direction of the integrated radio wave beam from the microstrip antenna by doing as described above, it becomes possible to detect the position and the state of the body more accurately, as compared with the case in which the direction of the integrated radio wave beam is fixed. For example, it is possible to ascertain whether a body is present or not over a two dimensional range, and the state thereof, by scanning the two dimensional range while changing the direction angles in the X and the Y directions of the integrated radio wave beam which is transmitted from the microstrip antenna. The use of such a body detection device spans many fields, such as target detection for an automatically tracking missile, user detection for a toilet device, and the like. Whatever the use may be, it is extremely useful to be able to change the direction of the integrated radio wave beam which is transmitted from the micro antenna. For example, to describe this in terms of a user detection device for a toilet device, if the position and the state of the user can be detected more accurately, it is possible to control a washing device or a deodorization device or the like of the toilet more appropriately. By the way, it might be more suitable to apply a camera, if only the objective of accurately ascertaining the state of the user is considered, but naturally a camera cannot be employed for a toilet device. Furthermore, with a body detection device which utilizes radio waves, it is extremely important to control the direction of the integrated radio wave beam, in order to make it possible to ascertain the situation of the user more accurately. In this connection, in Japan, the frequencies of 10.525 GHz and 24.15 GHz may be used with the objective of detecting a human body, and moreover the frequency of 76 GHz may be used with the objective of on-vehicle collision prevention.